ABSTRACT Each year, 700,000 - 900,000 burn patients develop severe hypertrophic scarring (HS). These scars restrict movement, are painful, and severely limit the quality of life for these patients. In small studies, we and others have found that Oxandrolone (OX) may improve burn wound healing and reduce post-burn HS. Preliminary experiments demonstrate that burn injury alters the expression of androgen receptors (AR) in the scar, and leads to changes in AR-mediated signaling in whole skin cultures and in fibroblasts from HS. In other cutaneous disorders, AR signaling has been found to be detrimental to wound healing. The effects of chronic androgen stimulation with OX on HS in the severely burned have not been studied. The over-arching hypothesis for Project 2 is therefore that delayed WH and severe HS result from androgen depletion after burn injury disrupt wound healing and lead to scarring, and that administration of OX improves WH and decreases HS by correcting these deficits. We propose that impaired WH related to compromised AR signaling is due to heightened inflammation in the wound and scar and decreased type II epithelial-to- mesenchymal transition (EMT) responses, and that defects in AR signaling lead to increased fibrosis (characterized by greater deposition of collagen), resulting in severe HS. We further hypothesize that long-term supplementation with OX will decrease local inflammation and restore AR signaling, improving WH and decreasing HS. This hypothesis will be tested by pursuing three Specific Aims that investigate the molecular events occurring in the skin and scars of the severely burned treated with and without OX to improve post-burn WH and HS outcomes. Aim 1 is to determine the effects of OX supplementation on WH and HS by measuring wound healing, scar severity, range of motion, fibrosis, and angiogenesis. Aim 2 is to quantitate the effects of OX administration on scar composition, by determining cellular composition and AR expression in the wound and scar, measuring pro-and anti-fibrotic factors that regulate fibrosis, and studying the role of the AR in key signaling pathways related to wound healing and scarring (EMT, inflammation, and angiogenesis). Aim 3 is to determine the effects of OX administration on Nuclear Factor kappa B (NF?B) regulation and the EMT. We will use patient biopsy samples and primary cell cultures to characterize the regulation of these pathways. Development of a therapy to improve post-burn wound healing and decrease scarring would improve the quality of life for severely burned patients, and reduce the long-term cost of their surgical and psychological care. Therefore, determining whether long-term supplementation of androgens improves WH and reduces HS in severely burned patients is a high priority.